Micrococcus luteus strains at a dose of 500 μg of whole cells caused anaphylactoid reactions leading to death in some instances within 1 h in C3H/HeN mice primed with muramyl dipeptide (MDP, 100 μg). Tumor necrosis factor (TNF) and interleukin-6 (IL-6) were induced in the serum of half and of all the surviving mice, respectively. Cell wall specimens of M. luteus so far examined also caused anaphylactoid reactions accompanied by early death and one strain induced high levels of TNF and IL-6. Cytoplasmic membranes also induced IL-6. Essentially similar results were obtained with representative M. luteus cells and a cell wall specimen in MDP-primed C3H/HeJ mice. These results indicate that M. luteus has virulence activities that are associated with the induction of septic shock and systemic inflammatory diseases.
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